1. Field of the Invention
The present invention relates generally to a port expansion system for connecting a single port, such as a USB port, on a host system such as a personal computer (PC) to various computer peripheral devices and functions, and particularly to such an expansion system that is user configurable so as to provide a high degree of flexibility and efficiency in the connection of the host system to a wide selection of peripheral devices and functions.
2. Description of the Prior Art
Although the invention and its background will be described chiefly in the context of the USB standard bus interface or protocol, it will be evident to those skilled in the art that the invention may be used with other standard bus interfaces including IEEE 1394, also called xe2x80x9cFirewirexe2x80x9d or xe2x80x9ci.Linkxe2x80x9d, and SCSI.
The difficulty of connecting and properly operating the many different kinds of personal computer peripheral devices and functions such as printers, scanners, digital cameras, modems, disk drives, and so forth, led to the adoption of the Universal Serial Bus (USB) standard which provides a hot pluggable, xe2x80x9cplug and playxe2x80x9d, cascadable serial interface using a low cost standard socket for adding external peripheral devices and functions. The Universal Serial Bus Specification Rev. 1.1 dated Sep. 23, 1998 is incorporated herein by reference in its entirety. Because power as well as data are transmitted through USB cables, some low power devices can be operated without the need for separate power adapters. The USB specification allows up to 127 peripheral devices to be connected to a single PC using USB hubs and defines how these peripheral devices can be connected together so that a host can use the resources provided by each device. USB ports are already found on many new PCs and a wide variety of USB peripherals are already on the market. Legacy-free PCs with one or perhaps two USB ports to connect peripherals are also becoming available. Such PCs do not incorporate traditional, standard interfaces.
There are currently available numerous converters for connecting a USB port on a PC or USB hub to traditional interfaces including serial ports, parallel ports, RJ-45 Ethernet LAN ports, and RJ-11 modem ports. These converters may also include one or more USB ports. However, the converters are housed within individual enclosures requiring a separate cable to attach each enclosure to a host system or to a hub.
Also presently available are multifunction USB hubs. For example, one such multifunction hub expands a USB-enabled PC to provide four additional USB ports along with three traditional ports consisting of two serial ports and one parallel printer port. However, such a multifunction USB hub is integrated into a single housing so that only a fixed number and combination of peripheral device or function ports is made available.
Broadly, the present invention provides a user configurable, modular port expansion system allowing the user of a host system such as a USB-enabled PC to customize a desired configuration of one or more peripheral device or function modules without the use of cables between modules. The peripheral device modules are physically and electrically connectable to each other side-by-side between first and second end modules in any sequence so that there can be provided, within the limits of the host system port specification, virtually any number of selected, expanded functions in any combination. The peripheral device modules may include, by way of example, a standard parallel DB-25 port module, a two-port serial PS/2 module, a two-port serial DB-9 module, a four- or seven-port USB hub, an RJ-11 Ethernet LAN module, and an RJ-11 modem module.
The invention further provides for the releasable or detachable coupling of the various peripheral device modules. Thus, the user can easily connect and separate the modules manually to readily custom design and assemble any desired combination and number of peripheral device modules within the limits of the host port specification. The mechanical coupling between adjacent modules includes mating connectors which also serve to transmit the required electrical signals between the individual device modules of the port expansion system and between the port expansion system and the host system thereby eliminating the need for external hubs and individual cables to the various modules. A technique for passing signals between the peripheral device modules allow the peripheral device modules to be connected together in any sequence, thus allowing a user to custom-configure a port expansion system to the user""s individual requirements. In addition, the system can be disassembled and the peripheral device modules reassembled in a different order if desired. By making available a variety of individual peripheral device modules, a user can purchase and add such modules to an existing system in building block fashion to mix and match peripherals and network connections.
More specifically, in accordance with the invention, there is provided a modular port expansion system for connecting peripheral devices to a host system, the host system including a host port providing a communication link for signals compliant with an industry standard protocol. The port expansion system comprises a hub module including a host port connectable to the host port on the host system; a downstream connector defining a plurality of slave ports, each slave port providing a communication link for signals compliant with the industry standard protocol of the host port on the host system; and a hub module interface circuit interconnecting the host port and the plurality of slave ports. The system further includes a peripheral device module for coupling a peripheral device to the hub module, the peripheral device module being directly connectable to the downstream connector on the hub module. The peripheral device module includes a peripheral device port, connectable to the peripheral device, providing a communication link for signals compliant with an industry standard protocol which may be the same as or different from the protocol of the host port on the host system. The peripheral module further includes an upstream connector releasably mateable with the downstream connector on the hub module, the upstream connector defining a plurality of ports corresponding to the slave ports defined by the downstream connector on the hub module. The upstream connector on the peripheral device module and the downstream connector on the hub module provide a direct, mechanical and electrical interconnection between the hub and peripheral device modules. The peripheral device module incorporates a peripheral device interface circuit connected between one of the ports on the upstream connector and the peripheral device port. Last, the peripheral device module has a downstream connector for mechanically and electrically connecting the peripheral device module directly to a releasably mateable upstream connector on another module.
In accordance with another aspect of the present invention, the plurality of ports defined by the upstream connector on the peripheral device module includes a first port, a second port and successive ports and the downstream connector on the peripheral device module defines a plurality of ports including a first port and successive ports. The first port on the upstream connector is connected to the interface circuitry of the peripheral device module. The second and successive ports defined by the upstream connector on the peripheral device module are sequentially connected to the first and successive ports on the downstream connector of the peripheral device module, along the lines of a xe2x80x9cshift onexe2x80x9d architecture. In this way, peripheral device modules can be connected together in any sequence.
A port expansion system in accordance with the present invention further includes a power end module connectable to the hub module, or to a peripheral device module, and which forms the end of the port expansion system opposite that of the hub end module. The power end module includes a connector for connection to an external power supply for powering the system in the event the system requires power above a predetermined level. The power end module may also include an expansion port for daisy chaining port expansion systems or for direct connection to one or more peripheral devices.
In accordance with a preferred embodiment, the port expansion system of the present invention utilizes standard, mateable DB-25 connectors for providing electrical and mechanical coupling between adjacent modules. Although the mechanical interconnection between adjacent modules afforded by the mateable DB-25 connectors provides sufficient structural integrity, such mechanical joinder of adjacent modules is preferably supplemented by means for releasably latching the modules together. The combination of the mechanical interconnection provided by the DB-25 connectors and the latching means results in a structure that has the rigidity and sturdiness approaching that of an integral or one piece unit, and creates the appearance of a one piece or solid block construction, yet nevertheless permits easy manual separation of the modules.